NATUEAL HISTOEY OF THE EED COEAL. 
69 
One of poly^ites may choose to withdraw from exposure 
to the surrounding water_, and he can carry out his desires 
without considering the opinions of his neighbours. He can 
extend his tentacles and body or retract them as it suits his 
pleasure^ without affecting his fellow ijolijpites. Hence it 
follows that he possesses a species of individuahty ; and yet 
he is only a member of a community connected by the closest 
organic relationship. His fleshy framework is continuous 
with that of the other members of the fraternity. He cannot_, 
therefore^ be regarded as an entire animal^ but only as a 
portion of one_, which is^ so to speak^ functionally independent; 
' that is to say^ a h and c, though each is capable of feeding 
and exercising himself^ is still part of one creation^ which we 
may write down as ahc. The separate ijohjpite is to the 
entire colony as the flower of a plant is to its fellow flowers^ 
and to the leaves^ branches^ and stem which compose the 
vegetable. If we were to endow the flower with the faculty 
of procuring and digesting food^ we should convert it into a 
polypite. The following tabular arrangement will convey an 
idea of what we mean : — 
Coral. 
Hard mineral framework. 
Soft fleshy covering. 
Polypites. 
Plant. 
Hard woody stem. 
Soft hark and cambium. 
Flowers. 
The Siamese twins form a good analogy. One polypite 
can perform movements independently of his brother_, but he 
cannot move away from him. Likewise he can feed_, but in 
both cases poison taken in by the one would be destructive of 
the other or others. 
Having said so much in regard to the external form and cha- 
racters of these animals^ we may now proceed to examine their 
general and microscopic anatomy^ and the modes in which they 
perform their various functions. It will be necessary at the 
outset to employ definite terms in order to avoid confusion. The 
fleshy covering which is of brick-red colour will be spoken of as 
the Sarcosome{(7ap^, flesh; and o-m/.m^body); the hard calcareous 
frameworkasthePoZypidom(poZ^j9i;s^polyp; and domus, house); 
and the entire colony as the Zoanthodeme animal ; avBog, 
flower ; and ^ryuLogj the people). Then again^ since there are two 
modes by which these animals can increase^ viz._, b}^ budding 
and by egg, we shall term the individual originated by the first 
process a bud-polypite and that by the latter an egg-polypite. 
The polypite is not merely contained within the cup- shaped 
depression (calyx) of the sarcosome, but is absolutely connected 
with it at its base, and when it is retracted is completely 
covered by it. On looking at one of the papillary elevations 
